Identification of Carbon dioxide (CO2) level is critical and important function of a Heating/Ventilation/Air-conditioning (HVAC) duct system. Typically, for measuring carbon dioxide (CO2) level, carbon dioxide (CO2) detectors/sensors are employed in the building. Based on reading from the carbon dioxide (CO2) detectors/sensors, the flow of fresh air can be increased or reduced into a particular part of the building.
Generally, CO2 sensors for ventilation control are of two type i.e. photometric and photoacoustic. The photometric sensors have a sample compartment that contains a photodetector, a light source and an optical filter. The light source emits light in the infrared range and the optical filter ensures that only wavelengths in the absorbing spectrum of CO2 enter the compartment containing the air sample. The photodetector measures the light intensity at a wavelength that may be absorbed by CO2. The higher the CO2 concentration in the sample air, the lower the measured light intensity.
The photoacoustic sensors have a sample compartment that contains a microphone and a light source for emitting infrared energy. The CO2 molecules in the compartment absorb the infrared energy, which in turn increases the molecular vibration and generates an acoustic field. The microphone picks up the acoustic field and converts it to an electronic signal identifying the CO2 concentration.
However, known CO2 detectors face one or more issues such as interference from other gases (e.g. water vapor), accuracy and drift that may affect the sensor performance. Moreover, CO2 detectors are very costly, require periodic maintenance and are not very accurate. Therefore, there continues to be a need for maintenance free, cost effective and more accurate system and method for detecting CO2 in a building.
The present invention is directed to overcoming one or more of the problems as set forth above.